[FIX] Success toast shows up when "Custom Sound" upload fails

[PriyaBihani]

• I have read the Contributing Guide
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Proposed changes (including videos or screenshots)

While adding a custom sound in the administration, if user uses an invalid name the success toast shows up along with the other error toasts. This PR introduces a check so that false success alert doesn't show up but only error toasts show up.

Previously

Screen.Recording.2021-04-21.at.2.45.16.PM.mov

Now
Success toast doesn't show up

Issue(s)

Steps to test or reproduce

1. Go to the administration panel.
2. Go to custom sounds.
   3)Add a custom sound with invalid name.

Further comments

[PriyaBihani]

@tiagoevanp can you merge this?

[CLAassistant]

All committers have signed the CLA.

[dougfabris]

@PriyaBihani thanks for your contribution! Already fixed here #25128